372 PROFESSOR A. CRUM BROWN AND DR JAMES WALKER ON THE 



The acid obtained from the pure calcium salt was solid and crystalline. It fused at 

 41°-42°. The fusing-point of ethylcrotonic acid is 41°. # 



Combustion gave the following results, agreeing with the formula C 6 H 10 O 2 : — 



01285 gramme of the acid gave 02969 gramme C0 2 and 0"1027gramme H 2 0. 

 Calculated for CgH^Oj. Found. 



C . . . 6316 6302 



H . . . 8-77 8-88 



For further identification of the acid we prepared the dibromide, using the method 

 described by Fittig and HowE.t At first the bromine in carbon disulphide solution was 

 immediately decolorised, afterwards more slowly. A mere trace of hydrobromic acid 

 was produced. A pale yellow crystalline mass remained after the carbon disulphide was 

 all evaporated. On recrystallisation from carbon disulphide the dibromide was obtained 

 in perfectly clear transparent crystals, fusing at 80°. Fittig and Howe give 80° "5 as 

 the fusing-point. 



The formation of ethylcrotonic acid from diethylmalonic acid may be represented by 

 the following equation : — 



C 2 Hr C 2 Hc C 2 H, 



I I I 



2CH 3 CH 2 CCOOC 2 H 5 = CH 3 C:OCOOC 2 H 6 + CH 3 CH 2 CCOOC 2 H 5 + C0 2 



COO- COOH 



The yield of low-boiling compound ethers is much smaller in the case of methyl- 

 malonic acid and of ethylmalonic acid than in that of the dialkylmalonic acids. From 

 the former we should expect to obtain ethyl acrylate, and from the latter an ethyl 

 crotonate. We have, however, not been able with certainty to isolate the corresponding 

 acids from these ethers. It would seem that these acids occur in the products mixed 

 with other acids, and that it would be necessary to work with very large quantities of 

 material in order to obtain them in a state of purity. 



By the electrolysis of ethyl-potassium methylmalonate we obtained 5 grammes of a 

 compound ether boiling between 100° and 105°. This we saponified with caustic potash, 

 and recrystallised the potassium salt from alcohol. The salt, which was very deliquescent, 

 contained, after drying over sulphuric acid, 31*9 per cent, potassium. Potassium acrylate 

 contains 35 "4 per cent, potassium. The compound ether decolorised bromine solution 

 somewhat slowly, the acid even more slowly. The acid had a very penetrating odour. 



From ethylmalonic acid we obtained about 8 grammes of a compound ether boiling 

 between 130° and 150°. It was saponified with caustic potash, and the acid was separated 

 in the usual way. This acid was liquid and miscible with water in all proportions. We 

 tried to purify it by converting it into the barium and the calcium salts. The barium 

 salt crystallised in small scales from water, in which it is easily soluble. The calcium 

 salt is more soluble in cold than in hot water. The barium salt dried at 130°, contained 

 43 "8 per cent, barium. Barium crotonate contains 44 "6 per cent, barium. The calcium 



* Fittig and Howe, Liebig's Annalen 200, 23. t Liebig's Annalen 200, 35. 



